Powdery mildew of cucumber – causal agents, disease management and introduction of a web application for disease assessment

Abstract

Powdery mildew of cucurbits is distributed worldwide. In Europe, the disease is mainly caused by the two species Podosphaera xanthii (syn. Sphaerotheca fuliginea, S. fusca) and Golovinomyces orontii (syn. Erysiphe cichoracearum). In this contribution, the current state of research on alternative agents for control of cucumber powdery mildew like salts, microorganisms and other agents of natural origin is shortly reviewed. In addition, an overview is given on measures available for regulation of cucumber powdery mildew in practical horticulture. Finally, a new web application for assessment of powdery mildew on cucumber leaves is introduced. It facilitates the training of disease assessment by random presentation of 67 computer-constructed drawings belonging to one of three classes, low (up to 15%), medium (10–40%) and high (more than 30%) disease severity. Furthermore, the disease progress can be simulated by presenting a film-like sequence of the 67 computer-constructed drawings in the order of increasing disease severity. The web application for powdery mildew of cucumber is presented under the URL http://prozentualer-befall.jki.bund.de, together with ten already existing equivalent schemes for cereal diseases.